Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
h,w = map(int, input().split())
maze = [list(input()) for _ in range(h)]
def repaint(maze,sx,sy):
  maze[sy][sx] = 1 
  que = deque([(sx,sy)])
  dxdy = [(1,0),(0,1),(-1,0),(0,-1)]
  while que:
    x,y = que.popleft()
    for dx,dy in dxdy:
      if 0<=x+dx<w and 0<=y+dy<h and maze[y+dy][x+dx] == ".":
        maze[y+dy][x+dx] = maze[y][x] + 1
        que.append((x+dx,y+dy))
  return True
white = 0
for x in maze:
  white += x.count(".")
repaint(maze,0,0)
if maze[h-1][w-1] == ".":
  print(-1)
else:
  print(white-maze[h-1][w-1])